You have definitely gotten better , and knowing that you have no teacher to help, this is very admirable progress on your part.
I see that you are more comfortable in the E saddle, not so stiff and not clamping with the knees.
When you cantered I saw that your lower body was not as loose and able to follow the motion as I bet it is in a W saddle. So, do it again and pretend you are in a W saddle an let your lower back/pelvis follow the motion a bit more. So you won't bump out of the saddle.
The horse worries a lot about the contact, doesn't she? I would try a bit of rding her with both more and less contact. Less contact can mean a totally looping rein. Might even try putting heavy rope reins on her , ride her with no contact at all unless you need it. The idea being that you work soley on posting without the benefit of any balancing on the reins. You would incorporate what Puck said about setting a rythm and sticking with it.
The way you have contact now, it's a bit inconsistent, so making it a bit stronger (shortening the reins) might help. You'd have to put more leg on, too.
AND, the mare is being over bent to the inside and drifting out through her outside shoulder.
Try riding her with basically ONE rein; the outside. Keep it pretty stead and use it against the neck to turn her to the inside if you need to. Use the inside rein almost not at all, but if you need to remind her to bend to the inside, you can put a little tickly on it and ask her to flex to the inside. But keep your outside rein on constant contact. You still have to follow the mouth, but never let it "gap", and don't let her "break" at the base of the neck. I mean don't let her kind of jacknife where her neck goes left and her shoulders go right. Know what I mean?